VENSET is a VENtilation Sytems Evaluation Tool for dwellings and is the final result of IEA Annex 27 evaluation and demonstration of domestic ventilation systems.The main idea for this annex was to develop tools to better evaluate domestic ventilation systems in dwellings in various situations. Different systems in various climates must handle situations with a large range of residential behaviour.
This paper describes the development of a simplified tool which should be used at the early design stage for predicting air ventilation rates in a building. The method is based on the assumption that the air flow rate may be calculated as a function of two independent parameters. The first, called effective pressure difference, takes into account the local weather data, surrounding terrain, and building typology. The second is the overall building permeability, and accounts for permeable components (geometry and permeability), including vents.
Experimental U-values based on measured heat flows through the walls of some houses have been found to be significantly higher than predicted by conventional calculation procedures. The work was carried out in ordinary occupied houses, and included measurements on party, internal and external walls. There are a number of possible reasons for the differences including thermal bridging, high thermal conductivities and excessive air movement in the wall cavities and behind plasterboard dry lining.
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